Chicken photoreceptor material will be studied by methods that have been employed to separate and characterize bovine rhodopsin in order to obtain information about the composition, structure, and function of iodopsin. Studies on phosphorylation and selective proteolysis of rhodopsin are underway to provide information about structural and functional characteristics or rhodopsin in the photoreceptor membrane. The experience and knowledge gained in these studies will be applied in the isolation of cone pigment and in comparing these pigments with rhodopsin, the rod pigment.